Method for production of aluminum chloride derivatives

ABSTRACT

Aluminum chlorohydrate products comprise particles of aluminum chlorohydrate in fractured crystal form, the particles having a basicity in the range of 0% to about 85.6%, and a surface area to weight ratio of about 295 to about 705 m 2 /kg, inclusive of both endpoints and all numerical values therebetween, where the ratio is measured by laser diffraction. Methods of producing such products are also disclosed.

RELATED APPLICATIONS

The present application claims the benefit of U.S. provisionalapplication Ser. No. 62/049,457, filed Sep. 12, 2014, which applicationis hereby incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to the production of a family of dryaluminum chloride, products ranging from zero percent basic, aluminumchloride hexahydrate (HEX), to 85.6 percent basic, aluminumchlorohydrate (ACH) using non-elemental sources of raw materials throughthe use of an improved process of treating HEX to produce dry aluminumchloride products of specific basicity.

BACKGROUND

In the aluminum chloride market there is a demand for products rangingfrom solutions that contain free hydrochloric acid to products, bothliquid and dry, of increasing levels of basicity. Aluminum chloride hasthe general chemical formula of Al_(n)(OH)_(m)Cl_(3n-m). Basicity isdefined as the ratio of

$\frac{m}{3n}.$where m is less than or equal to 5.2.

It is undesirable to use elemental aluminum as the source of aluminum toproduce these products due to the controlled availability and volatilityof pricing of the metal on the commodity market. Sources of aluminumsuch as aluminum ore (bauxite), refined aluminum ore (aluminumtrihydrate (ATH)) or various pre-solubilized forms are more desirablebecause of their availability and relatively stable pricing.

Production of high basicity products starting with aluminum fromnon-metallic sources requires rapidly increasing amounts of energy asbasicity increases. In addition to the energy, the stability of thefinal product begins to decrease once the basicity ratio is greater than0.3. From this point (0.3 basicity ratio) up to a basicity ratio of 0.83technology similar to that disclosed in U.S. Pat. No. 5,985,234 can beused, typically with aluminum metal as a starting material.

An alternate approach for increasing the basicity ratio is to removechloride from the molecule rather than adding aluminum. Under thisapproach, a simple solution of aluminum chloride is produced using anon-elemental source of aluminum. It is known that solutions of aluminumchloride when concentrated beyond saturation form crystals of aluminumchloride hexahydrate and that these crystals, when exposed to heat,decompose, releasing hydrogen chloride and water. This approach has beenapplied to produce high purity aluminum oxide and, to a lesser extent,to produce basic aluminum chloride, but only in batching operations. Aprocess that reduces the requirement of batching operations would resultin increased efficiency of production, lower cost, and improved safety.

Several publications describe systems that utilize mills and rotationalmotion for dehydration and drying materials. See e.g., U.S. Pat. Nos.6,145,765; 5,167,372; 4,390,131; 3,462,086; 2,470,315; and U.S.publication number 2004/0040178. These systems do not address issuesassociated with the stringent requirements, such as handling of evolvedhydrochloric acid that must be addressed in the production of aluminumchloride products of specific basicity. In another approach, flash dryersystems involve spraying slurry onto a dryer and applying hightemperature to evaporate gas and liquid components. See e.g., U.S. Pat.No. 5,573,582.

Evaporation, crystallization, and recovery of formed crystals are wellknown in the art. See for example, McCabe and Smith 1976, UnitOperations of Chemical Engineering, in particular, the followingsections: Evaporation, pages 425-463 to 11-118, Crystallization, pages852 to 894, and Filtration, pages 922 to 953; and Perry's ChemicalEngineering Handbook (7^(th) Ed. Perry and Green, 1999), sections:Evaporation, pages 11-107 to 11-118, Crystallization, pages 18-35 to18-55, and Filtration, pages 18-74 to 18-125.

SUMMARY OF THE EMBODIMENTS

Embodiments disclosed herein include aluminum chlorohydrate productscomprising particles of aluminum chlorohydrate in fractured crystalform, the particles having a basicity in the range of 0% to about 85.6%,and a surface area to weight ratio of about 295 to about 705 m²/kg,inclusive of both endpoints and all numerical values therebetween, wherethe ratio is measured by laser diffraction. In a related embodiment, thefractured crystal particles have a mean particle size in the range ofabout 10 to about 15 microns. In a further embodiment, the particleshave a basicity of about 83% and a surface area to weight ratio in therange of about 575 to about 700 square meters per kilogram, as measuredby laser diffraction. In another related embodiment, the fracturedcrystal particles have a basicity of about 50%, about 60%, about 72%,about 83%, or about 85%.

Embodiments disclosed herein also include a method for producingaluminum chloride hexahydrate particles of a desired basicity thatincludes applying a high temperature gas stream to a circular mill toestablish and maintain a circulating gas stream within the mill at aconstant temperature. Aluminum chloride hexahydrate crystals areintroduced into the heated circular mill, where the crystals are formedinto aluminum chlorohydrate particles and separated based on particledensity. The resulting particles having a basicity that is a function ofthe constant temperature, and are dried and collected as they exit thecircular mill. In a related embodiment, constant temperature is in therange of 200° F. to 400° F. and the dried particles collected from themill have a basicity range of about 50% to about 85.6%. In a furtherrelated embodiment, the constant temperature is in the range of 220° F.to 240° F. and dried particles comprise Al₂O₆ with a basicity of 0 to5%.

In another related embodiment, the constant temperature is in the rangeof 260 to 280° F., and the particles comprise Al₂(OH)Cl₅ with a basicityof about 14 to 18%. In a further related embodiment, the constanttemperature is about 300-310° F. and the dried particles compriseAl₂(OH)₂Cl₄ and have a basicity of about 31 to 35%.

In another related embodiment, the constant temperature is about340-350° F. and the dried particles comprise Al₂(OH)₃Cl₃ and have abasicity of about 38 to 52%. In a further related embodiment, theconstant temperature is about 350 to 360° F. and the dried particlescomprise Al₂(OH)₄Cl₂ and have a basicity of about 64 to 68%. In yetanother related embodiment, the constant temperature is about 380 to400° F. and the dried particles comprise Al₂(OH)₅Cl and have a basicityof about 81 to 85%.

In another related embodiment, the gas stream comprises ambient air andsteam.

In yet another related embodiment, the dried particles have a bulkdensity of about 40 to about 65 pounds per cubic foot; and/or a surfacearea greater than about 300 square meters per kilogram and less thanabout 700 meters per kilogram; and or a surface area of greater than 500square meters per kilogram and less than 600 meters per kilogram.

In an embodiment of the invention, there is provided a method forproducing. aluminum chloride hydrates of various basicity; the methodincludes applying a high temperature gas stream to a circular mill tomaintain a constant temperature creating a heated circular stream;feeding a HEX particle into the circular mill, wherein the HEX particlesbegin to decompose forming particles of various basicities anddensities; centrifugal forces inside the circular mill cause theparticles to separate based on particle density; varying feed rate tomaintain a constant exit temperature; and collecting dried particles asthe particles exit the circular mill.

Embodiments of the invention also include aluminum chlorohydrateparticles produced by the methods described herein and/or with one ormore particle properties described herein, including basicity in therange of 0% to about 85.6%; surface area to weight ratio of about 295 toabout 705 m²/kg; and a bulk density of about 40 to about 65 pounds percubic foot.

The aluminum chloride products described herein are produced efficientlyusing methods and systems that greatly reduce the energy required toprepare aluminum chloride products having a desired basicity, andtherefore a corresponding reduction of production costs.

Embodiments of the invention also include methods for utilizing thealuminum chlorohydrate particles described herein in applications suchas waste water treatment, manufacture of catalyst support systems, andother applications of aluminum chloride products.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of embodiments will be more readily understood byreference to the following detailed description, taken with reference tothe accompanying drawings, in which:

FIG. 1 is a flow diagram of a method for the production of aluminumchloride of various basicities in accordance with an embodiment of thepresent invention.

FIG. 2 is a schematic representation of a one embodiment of a system forthe production of aluminum chloride hydrates of various basicities inaccordance with the method of FIG. 1.

FIG. 3 is a graph (A) showing results of particle size distributionanalysis of aluminum chloride particles produced by milling (firstpeak), spray drying (second peak), or using a fluid bed dryer (thirdpeak). Also shown is a table (B) showing numerical values of theparticle size distributions. The aluminum chloride particles produced bymilling were produced in accordance with an embodiment of the presentinvention, and have a basicity of about 83%. The particles produced byspray drying were produced by prior art methods. Similarly the particlesproduced using a fluid bed dryer were produced by prior art methods.

FIG. 4 shows results of scanning electron microscopy (SEM) of the priorart aluminum chloride particles produced by spray drying (whichparticles are also a subject of FIG. 3), the SEM picture includingparticle size markings.

FIG. 5 shows results of scanning electron microscopy of the prior artaluminum chloride particles produced in a fluid bed dryer (FBD) (whichparticles are also a subject of FIG. 3), the SEM picture includingparticle size markings.

FIG. 6 shows results of scanning electron microscopy of the aluminumchloride particles produced by milling according to an embodiment of thepresent invention (which particles are also a subject of FIG. 3), theSEM picture including particle size markings.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Definitions. As used in this description and the accompanying claims,the following terms shall have the meanings indicated, unless thecontext otherwise requires:

Polyaluminum Chlorides: Polyaluminum chlorides are products of aluminumchloride hydroxide, AlCl(OH)₂, AlCl₂ (OH), and Al₂ Cl(OH)₅. Arepresentative formula is: Al₂Cl_(6-n)(OH)_(n), where n=2.7 to 5 forproducts formed via the process disclosed herein. It is thought that,when these products are diluted, polymeric species such as: Al₁₃O₄ OH)₂₄(H_(.2)O)12+7Cl are formed.

Basic Aluminum Chlorides: These are compounds having the formula:Al₂(OH)_(n) (Cl)_(6-n) where n is greater than zero and less than orequal to 1.5. It is believed that solutions of these compounds contain:Al(H₂O)₆+3Cl; Al₂(OH)₂ (H₂O)₈+4Cl; and Al(OH)(H₂O)₅+2Cl.

Aluminum Salt Concentration of Reaction Products: The concentration ofaluminum salt stated as present in a reaction product refers to theamount of aluminum oxide that would have been necessary to make theproduct. Thus, products are described as having a certain percentage ofAl₂O₃ even though the aluminum oxide may not actually be present in theproduct. This is common practice in the art and allows products to becompared based upon their chemistry.

Laser diffraction: Laser diffraction is a method of determining, amongother things, surface area per unit of weight, using optical diffractionas described in ISO 13320:2009 “Particle Size Analysis—Laser DiffractionMethods”.

Basicity: Aluminum chloride has the general chemical formula ofAl_(n)(OH)_(m)Cl_(3n-m). Basicity is the ratio of

$\frac{m}{3n}$where m is less than or equal to 5.2.

The invention summarized above may be better understood by referring tothe following description, the accompanying drawings, and the claimslisted below. The description embodiments, set out below to enable oneto practice an implementation of the invention, is not intended to limitthe preferred embodiment, but to serve as a particular example thereof.Those skilled in the art should appreciate that they may readily use theconception and specific embodiments disclosed as a basis for modifyingor designing other methods and systems for carrying out the samepurposes of the present invention. Those skilled in the art should alsorealize that such equivalent assemblies do not depart from the spiritand scope of the invention.

An optimized method for the production of aluminum chloride hexahydratecrystals is shown in the flow diagram of FIG. 1, and includes thefollowing steps: (1) Evaporation/Crystallization 200, (2) Crystalrecovery 220, (3) Crystal drying and/or decomposition 230, and (4)Crystal Collection and Processing 240.

(1) Evaporation/Crystallization 200

Aluminum chloride hexahydrate, crystals are created from an aluminumchloride solution, with evaporation of unwanted water with heat in thegeneral range of 230-250 degrees Fahrenheit. One method of performingthe evaporation/crystallization step 200 is in a batch system.

In an embodiment, a standard commercially available aluminum chloridesolution at a concentration of 10.7% Al₂O₃ or 28.0% Al₂Cl₆ is charged toan agitated process tank. The solution is circulated through an externalheat exchanger where process steam is used to raise the temperature ofthe solution to near boiling (between 230° F. and 235° F.). The heatedliquid is drawn through a venturi and back into the process tank wherevacuum from an induced draft fan causes localized boiling andevaporation of water from the system. The removal of water from thesolution causes the concentration of aluminum chloride to increase tothe saturation point of 12.4% Al₂O₃ or 32.4% Al₂Cl₆. When the solutionconcentration exceeds the saturation concentration, aluminum chloridehexahydrate (HEX) crystals begin to form. This process is continueduntil the volume of crystals in the recirculating solution exceeds 30percent by volume.

Once the 30 percent by volume crystal concentration is reached, thesteam flow is stopped and the solution is transferred into an agitatedcollection tank where it is cooled to between 160° F. and 180° F. toallow the crystals to mature and grow in size to nominally between 30and 40 Tyler mesh. This step facilitates removal of the mother liquorfrom the crystals in the recovery step that feeds the crystal recoverystep. The evaporator system is re-charged with aluminum chloridesolution and the process is repeated.

(2) Crystal Recovery 220

In the second step 220 of one preferred embodiment of the process, thealuminum chloride solution containing the HEX crystals is fed to a plateand frame filter where the crystals are separated from the solution. Thesolution is returned to the aluminum chloride storage tank that feedsthe evaporator system. Once the filter chambers are full of crystal, themother liquor contained in the cake is blown out of the crystal cakeusing compressed dry air at between 10 to 20 PSIG. The crystals are thendischarged from the filter are collected in a feed hopper equipped witha variable rate feeder.

(3) Crystal Drying and/or Decomposition—230

In a third step of the process 230, the variable rate feeder dischargesde-agglomerated aggregates into a flash energy drying/grinding mill 540.The drying/grinding mill 540 is a circular tube. In some embodiments thetube is elongated as shown in FIG. 2, however, it is contemplated thatother circular shapes may be utilized, but in all applications of thistechnology a system that applies centrifugal or gravitation forces toinduce particle separation based on density is required.

The drying/grinding mill 540 has an intake 585 through which the HEXfrom step 2 is introduced. The feed rate is varied to maintain aconstant exit temperature from the mill. This is important sincebasicity of the product is a time and temperature dependent reaction andis based on the amount of energy that can be absorbed by the HEX. Sincethe contact time inside the mill is short and consistent (5-10 seconds),maintaining the exit temperature of the mill 540 coupled with the gassupply temperature assists in producing the desired product.

Variations in free moisture of the feed to the mill affect theproduction rate of the product produced. As moisture increases, moreenergy is consumed to evaporate the moisture. With less energy present,the feed to the mill needs to be adjusted so that the ratio of dry HEXto energy absorbed is maintained to perform the decomposition reaction.

Because of the short residence time the feed is exposed to the thermalenergy inside the mill, constant adjustments to the feed rate must bemade to adjust for any variability of the feed stock, in order tomaintain a constant exit temperature from the system. This isaccomplished by use of a feedback control loop with the mill exittemperature 546 being the control variable, and the speed of the feeder550 being the control element. Typical product basicity in associationwith the mill 540 exit temperature of each product is shown below inTable 1.

TABLE 1 Mill Operating Temperature Ranges for Various ProductsTemperature Operating Range* Product Percent Basic Degrees FahrenheitAl₂Cl₆ 0 to 5 220 to 240 Al₂(OH)Cl₅ 14 to 18 260 to 280 Al₂(OH)₂Cl₄ 31to 35 300 to 310 Al₂(OH)₃Cl₃ 48 to 52 340 to 350 Al₂(OH)₄Cl₂ 64 to 68350 to 360 Al₂(OH)₅Cl 81 to 85 380 to 400 *Dependent on gas supplytemperature to mill

The energy is applied convectively in the mill and comes from heated airand/or superheated steam through tangential nozzle(s) 542, 543, 544. Theaddition of steam to the supply gas was found to increase the productionrate. In an embodiment, a portion of the air can be replaced with acondensable gas to ease the volume of HCl-laden gas on the recoverysystem. In a preferred embodiment, however, steam is used. This mixtureis supplied to the mill between 400° F. and 1,200° F. and producesvelocities inside the mill of between 3000 and 6000 feet per minute.

As the particles of HEX dry and/or decompose, they lose bulk density dueto the removal of water and HCl from the particle, making the crystallattice more porous. It is this porosity on the surface of the particlethat causes the internal portion of the particle to be insulated fromthe applied heat and thus resist decomposition. Collisions with otherparticles in the mill and impingement against the walls of the millprevent the crystals from agglomerating as the particles circulatearound the inside of the mill. Such collisions and movement also serveto scour finished product from the surface of the particles exposingwetter and/or less decomposed material to the energy in the system. Suchexposure presents a distinct and unexpected advantage over prior knownprocesses and makes the present process more beneficial over other knownmethods of manufacturing the desired products. Without this scouringand/or grinding in the mill, the outer surface of the particle willbecome over-decomposed, while the interior remains under-decomposed.Over-decomposed products become insoluble and thus useless productsand/or produce highly viscous solutions that are difficult to use orperform poorly in product applications.

Decomposition processes as described here and in prior art will producedilute acid solutions during production or when cleaning equipment. Animportant aspect of the products produced by the process describedherein is that these products can be made at higher than 83% basicity.The high basicity product can be diluted with the above acidic solutionsproduced by decomposition, and still generate a liquid ACH with abasicity above 83%. To our knowledge, this is not possible with anyprior known product, as material produced at an above average of 83%basicity will contain over-decomposed product in the exterior of theparticle and under-decomposed material in the center. This will generateinsoluble material that is extremely difficult to filter and result inloss of raw materials.

Currently commercial products of dry ACH are made by reacting aluminumchloride, basic aluminum chloride or hydrochloric acid with metallicaluminum. This generates a 50% solution of ACH which is then spraydried. This is an energy intensive process for all the water must beevaporated and production of metallic aluminum is energy intensive aswell. The product of this spray drying process is spherical crystals ofaluminum chlorohydrate dihydrate of which 90 percent are less than 71microns. See FIG. 3. Laser Light Diffraction has determined that theseproducts have a specific surface area of less than 100 square meters perkilogram. The small specific surface area may be limiting in theusefulness of the product as a dry chemical reactant. The two waters ofhydration also prohibit the use as a dry reactant in that the ACHdihydrate dissolves rapidly in cold water.

Products of the earlier Fluid Bed Dryer Technology also have smallspecific surface areas of less than 100 square meters per kilogram. Theyare long crystalline cylinders which 90 percent of the material is lessthan 369 microns. See FIG. 4. These products contain less than twowaters of hydration but lack the specific surface area for goodreactivity as dry reactant. The small surface area may cause longerreaction times which may be problematic in some reactions.

The products of this invention are fractured crystals of which 90percent are less than 17 microns. A specifically unique feature of theseproducts is the large surface area of the particles formed. See FIG. 6.The specific surface area of these products, at 83% basicity, based onlaser diffraction analysis, is in the range of about 575 to about 700square meters per kilogram. Since more water and hydrochloric acid arereleased from the hexahydrate crystal as basicity increases, it can bedemonstrated that the lower basicity products would have a smallersurface area than the higher basicity products. Table 2 belowdemonstrates what can be expected.

TABLE 2 % Basic Versus Surface Area Percent Basic Operating Temperature° F. Surface Area (m²/kg) 50% 345 295 72% 365 452 83% 395 607 85% 400705

If appropriate conditions are not maintained, the average of thedecompositions may be the desired value, but the standard deviation willbe wide producing a product that may not have the desired properties orstability. The centrifugal forces inside the mill cause the materialinside to separate based on particle density. The more dense material(wetter/less decomposed) will migrate to the outer radius of the milland away from the mill discharge 590 and are retained longer, while theless dense (drier/more decomposed) travel towards the inner radius ofthe mill and exit the system through the mill discharge 590 as thedesired product. The decomposition releases water and hydrogen chloridein gas form from the particles as they decompose.

The waters of hydration will vary with the basicity of the productproduced. Material of about 70% basicity have two waters of hydration,83% basicity has about half a water of hydration and the product becomestotally anhydrous at over 85% basicity. Commercially available ACH (83%basicity) has two waters of hydration.

(4) Crystal Collection and Processing

In a final step 240 crystals of the appropriate basicity are collectedand processed. The product exits from the mill discharge 590 and alsocontains hydrogen chloride and water in a gaseous form. Primaryseparation is performed by a cyclone separator 570. The dischargedmaterial from the cyclone will still contain hydrogen chloride gas andwater vapor. Before these components have an opportunity to condense andbe absorbed by the product they are stripped from the system by passingair through the product in a fluidized bed or by operating the cycloneunder vacuum conditions. Once the product is separated from the gasstream it is conveyed to a storage bin. Once in the storage bin theproduct is either packaged as is or sent to additional processing toproduce a liquid product.

One advantage over this process over previous designs with Fluid BedDryer (FBD) technology is the heavier bulk density of the product. Theheavier bulk density allows for less storage bin space and will requireless volume when shipped. The bulk density of ACH made from this processcan range from 55 to 60 pounds per cubic foot while material from a FBDsystem can range 18 to 25 pounds per cubic foot.

System Components

In one embodiment, a system for the production of aluminum chlorides ofvarious basicities is shown in FIG. 2. In the system, aluminum chloridehexahydrate crystals are put in a variable rate crystal feeder 550. Thevariable rate crystal feeder is connected to the grinding mill 540 by aconduit 501 that attaches to the mill's intake 585. Air, steam, or gasis supplied to the grinding mill 540. Ambient air is provided through anair supply blower 520 that is connected to an air heater 530. Steam issupplied through a steam supply source and a steam flow meter 510measures the initial flow of steam into the system. Steam supply flow iscontrolled by a steam flow control valve 511. Steam or gas and ambientair are mixed and delivered to mixed gas supply header 541. Mixed airpressure and temperature are measured at the blower and heater through amixed supply pressure meter 531 and a mixed gas supply temperature meter532.

Mixed air is then divided into a number of mixed gas feed nozzles, 543,543, 544. It is contemplated that the number of nozzles may varydepending on the size of the grinding mill 540. The product exits themill 540 at the mill discharge 590 which connects to a product conveyingline 560. Exit temperature and pressure are measured at the milldischarge 590 or product conveying line 560 by a grinding mill exitpressure meter 545 and a grinding mill exit temperature meter 546.

The product conveying line 560 delivers the product to the air/solidseparating cyclone 570. The air/solid separating cyclone 570 isconnected to a system induced draft fan 580. The system induced draftfan 580 assists in recovering excess air, water, and HCl. The air/solidseparating cyclone 570 deposits dry aluminum chloride product to theproduct air lock 572 and the product can then be collected.

Commercially available ACH is made by elemental digestion of aluminum inHCl or aluminum chloride solutions. The dried product is then commonlymade by spray drying ACH solutions, which is an expensive process. Whenusing such a system, it is advantageous to process particles of lessthan 100 microns in order to prevent clogging of aerosol sprayers. Thealuminum chlorohydrate products produced as described herein areproduced in a manner that eliminates the expensive spray drying step,yet yields small particles with a high surface area and at desiredbasicity.

The embodiments of the invention described above are intended to bemerely exemplary; numerous variations and modifications will be apparentto those skilled in the art. All such variations and modifications areintended to be within the scope of the present invention as defined inany appended claims.

The published patents and applications, and other published documentsreferenced in this description are hereby incorporated by reference intheir entirety.

What is claimed is:
 1. A method for producing aluminum chloride hydrateparticles of a desired basicity, said method comprising: applying aheated gas stream to a circular mill to establish and maintain acirculating gas stream within the mill at an operating temperature in arange of between 200° F. and 400° F.; feeding aluminum chloridehexahydrate crystals into the circular mill, wherein aluminumchlorohydrate particles are formed and the resulting particles areseparated based on particle density, the particles having a basicitythat is a function of the operating temperature; and collecting driedaluminum chlorohydrate particles as the particles exit the circularmill.
 2. The method of claim 1, wherein the dried particles collectedfrom the mill have a basicity range of 0 to 85.6%.
 3. The method ofclaim 1, wherein the operating temperature is in the range of between220 and 240° F.
 4. The method of claim 3, wherein the collected driedparticles comprise Al₂Cl₆ and have a basicity of 0 to 5%.
 5. The methodof claim 1, wherein the operating temperature is in the range of between260 and 280° F.
 6. The method of claim 5, wherein the collected driedparticles comprise Al₂(OH)Cl₅ and have a basicity of 14 to 18%.
 7. Themethod of claim 1, wherein the operating temperature is in the range ofbetween 300 and 310° F.
 8. The method of claim 7, wherein the collecteddried particles comprise Al₂(OH)₂Cl₄ and have a basicity of 31 to 35%.9. The method of claim 1, wherein the operating temperature is in therange of between 340 and 350° F.
 10. The method of claim 9, wherein thecollected dried particles comprise Al₂(OH)₃Cl₃ and have a basicity of 38to 52%.
 11. The method of claim 1, wherein the operating temperature isin the range of between 350 and 360° F.
 12. The method of claim 11,wherein the collected dried particles comprise Al₂(OH)₄Cl₂ and have abasicity of 64 to 68%.
 13. The method of claim 1, wherein the operatingtemperature is in the range of between 380 and 400° F.
 14. The method ofclaim 13, wherein the collected dried particles comprise Al₂(OH)₅Cl andhave a basicity of 81 to 85%.
 15. The method of claim 1, wherein the gasstream comprises ambient air and steam.
 16. The method of claim 1,wherein said dried particles have a bulk density of 40 to 65 pounds percubic foot.
 17. The method of claim 1, wherein the collected driedparticles have a surface area of greater than about 300 square metersper kilogram and less than about 700 meters per kilogram, as measured bylaser diffraction.
 18. The method of claim 1, wherein the collecteddried particles have a surface area of greater than 500 square metersper kilogram and less than 600 meters per kilogram, as measured by laserdiffraction.
 19. The method of claim 1, wherein the collected driedparticles have a mean particle size in the range of about 10 microns toabout 15 microns.